Package v1grid

Variant 1 grids. Extract from the compressed RDNAPTRANS(tm)2018_v229627 nlgeo2018.txt.zip and rdcorr2018.txt.zip grid files only columns NAP_..., lat_corr_ and lon_corr_ columns and encode each as a row-order matrix in Python, a 481-tuple of 301-arrays of single- or double precision floats.

Of the 144,781 floats (481 x 301) in the lat_corr_ and lon_corr_ columns of the rdcorr2018.txt grid file only 55,139 respectively 55,348 are non-zero between indices [8598:93827] respectively [8598:93830] (and 89,642 respectively 89,433 are zero).

As a result, the first 28 and the last 169 matrix rows (in total 197 rows or 41% of 481) are representable by the same 301-array of single-precision zeros. There are other runs of zeros, but none amount to 301 or more.